Before James fort was constructed, an earlier medieval fortification existed on the site. This fortification, named Castle Ny-Parke[4] was occupied for a time by Spanish forces during the early part of the Siege of Kinsale (1601). It was captured however from the Spanish by Sir Richard Smyth[5] who led the attacking English forces of Charles Blount, Lord Mountjoy.

Construction of James Fort commenced in 1602 - immediately after the Siege of Kinsale. The fort was named after James I of England and VI of Scotland, and was built to designs by Paul Ive (to replace and supplement the older medieval structure).[6] Completed by 1607, the central structure was a half-bastioned four-sided stone fortification, surrounded by pentagonal earthworks to a star fort design.[7] Tunnels linked a hexagonal "Block House" at the water's edge - an additional coastal artillery emplacement at the narrowest point in the channel.[8]

As with Charles Fort on the other side of the harbour, James Fort was occupied by Jacobite forces during the Williamite War in Ireland. It was captured however in 1690 by Williamite forces, after being damaged by an explosion of gunpowder stores.[9]

Though Charles Fort (the "new fort") was operated as a military garrison through to the early 20th century, James Fort (the "old fort") declined in use in the 18th century, and texts and maps describe it as a ruin by the early to mid-19th century.[10]